The present invention relates to an injection mould and methods for making the same.
It is time-consuming and expensive to design and make injection moulds. Usually a mould maker obtains a three-dimensional digital product pattern of the product. Then the mould maker adjusts the product pattern so as to obtain a mould pattern that can be used for making a product cavity by means of an NC machine. This adjustment of the product pattern is only necessary if the pattern has such deficiencies that it could not be used for making a product cavity by means of an NC machine, such deficiencies being quite common.
Subsequently the mould maker must take undercuts and various other mould-specific and mould injection technical parameters into consideration to find the most convenient design for splitting or parting as regards the movable and the fixed mould half.
Once a suitable splitting/parting has been achieved, the mould maker begins to plan and design the movable parts of the mould, such as sliders, and to plan bores for cooling channels as well as ejectors.
The forming of bores for cooling channels in each mould half must be carefully considered in order to achieve adequate cooling which is adapted to the product mould in question. The forming of bores for ejectors must also be carefully considered in order to provide ejection which is both gentle and efficient. Moreover, it must also be ensured that ejectors and cooling channels do not collide with each other, preferably while at the same time cooling or ejection must not be deteriorated.
When the mould has been planned and designed, the mould maker produces data for machining of the two mould halves. The data is usually ordinary two-dimensional construction drawings and data for NC machines. Then the machining of the two mould halves as well as mounting and fitting thereof take place.
An object of the present invention is to reduce the time it takes to make a mould from the point of time when a pattern of an intended product is received until the point of time when a completed mould can be presented.
This object is achieved by a method for making an injection mould according to claims 1, 8 and 11 as well as an injection mould according to claim 5. Preferred embodiments are stated in the dependent claims.
According to the invention, the method for making injection moulds comprises the steps of
receiving a product pattern,
defining function holes and function recesses, and
defining, separate from and parallel to the construction of function holes and function recesses, a product cavity and a parting plane of the mould.
By carrying out the defining of function holes and function recesses separate from and parallel to the defining of the product cavity and parting plane of the mould it is possible to save time since both the defining of function holes or function recesses and the defining of the product cavity are steps in the production process which take long. A further advantage of this mode of procedure is that the defining of function holes and function recesses can be begun as soon as a product pattern has been obtained even if the obtained pattern is not of such quality as to allow it to be used without adjustments and changes for the defining of the product cavity and the parting plane of the mould. In such a case, the defining of the product cavity and the parting plane of the mould must be preceded by the product pattern being xe2x80x9cmendedxe2x80x9d whereas the defining of function holes and function recesses can be carried out completely without the product pattern being xe2x80x9cmendedxe2x80x9d.
According to a preferred embodiment, all function holes and function recesses in a first pattern of the mould are defined while the product cavity is defined in a second pattern of the same mould. In this way, the work with the defining of function holes and function recesses can take place completely separate from the work with the defining of the product cavity and the parting plane of the mould.
According to a preferred embodiment, defining of function holes and function recesses comprises defining of cooling channels, holes for ejectors, grooves for driving of sliders etc.
Preferably, the mould patterns are digital patterns which can be changed and/or adjusted by means of a CAD program, Construction Aided Design. The step of defining, in connection with these patterns, function holes, function recesses, product cavity and mould parting plane can thus comprise designing of the pattern in question in a manner that is known to those skilled in the art.
According to the preferred embodiment, a coordinate system of the product pattern is defined before it is placed in one of the first and the second mould pattern. Preferably, the origin of said coordinate system is placed essentially in the centre of the product pattern. The advantage of defining this coordinate system of the product pattern is that it will be easy to place the product pattern in the respective mould pattern in a position corresponding to one and the same position in the completed mould. Thus, machining of the mould can be effected on the basis of data originating from the separate mould patterns without the use of two separate mould patterns causing difficulties in the positioning of components defined in the separate patterns.
Moreover, according to the preferred embodiment, the method comprises the steps of generating data regarding function holes and function recesses from the first mould pattern for machining of the intended injection mould, generating data regarding the product cavity and the parting plane of the mould from the second mould pattern for machining of the intended injection mould, machining a blank for the intended injection mould by means of said data regarding function holes and function recesses independently of the data generated from the second mould pattern, and machining a blank for the intended injection mould by means of said data regarding the product cavity and the parting plane of the mould independently of the data generated from the first mould pattern.
Thus, machining of the blank for the intended injection mould can be begun as soon as one of the defining processes has generated a sufficient amount of data to enable machining, which means that additional time can be saved.
According to the preferred embodiment, the injection mould comprises a plurality of modules. Preferably, the injection mould comprises at least five modules which are aligned with each other. The five modules are:
a first mould module and a second mould module for forming a product cavity,
a drive module for driving of sliders,
an engaging module adapted, by application of a force, to prevent dividing between the first and the second mould module when introducing product material into the product cavity, and
an ejector module for ejecting a completed product from one of the first and the second mould module.
By dividing the injection mould into several modules as stated above, the machining time for the mould can be reduced further. The reduced machining time is a result of the possibility of machining several modules in the mould simultaneously. It is even possible to machine all modules simultaneously and, since essentially all modules have a special function that is not designed in the same way in all modules, the module construction implies that machining that was previously necessarily carried out sequentially can now be carried out in parallel. For instance, a cooling channel in a module can be machined, while at the same recesses for driving of sliders can be machined in another module while at the same time guiding recesses for ejector pins are machined in another module, etc. Furthermore, the module construction makes it possible to easily and rapidly replace a damaged cavity since only the mould module has to be made again and all the data for machining is already available. The advantage of merely replacing a mould module with a new mould module is also applicable to products where the form is changed without affecting the location of ejectors and sliders. In such a case, all the other modules can be retained while new mould modules are made.
According to the preferred embodiment of the invention, a cooling channel is produced by removing material from the surface of a module until the cooling channel forms a continuous groove in the module. In operation, the groove is covered by an adjoining module, thus producing a channel for coolant. The advantage of making cooling channels in this way is that it is a quick operation and that the cooling channel can be given largely any form and extent.
Moreover, according to the preferred embodiment of the invention, the drive module comprises recesses for wheels and shafts for driving of sliders. Further the drive module has grooves intended to accommodate means connecting the wheel of a slider to a wheel for transmitting the motion. Said wheel is preferably a gear wheel, but can also be different kinds of belt drive wheels, and said means for connecting is preferably a chain, but can also be a drive belt of some kind or a plurality of gear wheels, intermediate gear wheels, which by directly engaging each other transfer force to sliders.
Preferably, the present injection mould is designed for injection moulding of three-dimensional products.
The order of the steps in the claims does not define an order of priority if this is not clearly indicated.